Placer mining sluices are conventionally used to separate relatively heavy particulate valuable materials such as gold dust, gold nuggets, silver, platinum, mercury or mercury-coated gold from relatively lighter waste materials. The mining operation is usually conducted near a stream or other source of flowing water. Raw material such as sand, gravel, mud or a mixture thereof which is believed to contain particulate valuable material is extracted from the stream bed (or other raw material source such as a pile of tailings accumulated from hard rock mining) and dumped into the mining sluice. Some water is diverted from the flowing stream (or a separate source of flowing water is provided) and caused to flow through the mining sluice, carrying with it the raw material from which particulate valuable material is to be separated. A grizzly screen is typically provided to prevent bulky material (rocks or other objects having a diameter in excess of about 1/4 inch) from entering the mining sluice. After passing through the grizzly screen, the water/raw material mixture flows over one or more inclined trays. Matting and screening placed upon the tray surface(s) traps relatively heavy particulate valuable materials. Periodically, the miner stops the flow of water and raw material through the mining sluice and extracts therefrom any valuable materials which may have accumulated on the tray surfaces.
One disadvantage of conventional mining sluices has been the loss from the sluice of a relatively large amount of raw material from which particulate valuable materials might possibly have been separated. For example, gaps in the mining sluice structure often permit raw material to escape from the mining sluice apparatus without passing over the tray surface(s). Accordingly, one object of the present invention is to provide a mining sluice which is designed to enable the operator to maximize retention of raw material within the mining sluice apparatus for passage over the tray surface(s).
A second disadvantage of conventional mining sluices has been their relatively cumbersome structure which makes it difficult or time consuming to transport the mining sluice to and from a mining site (which will typically be located in rugged country). Such cumbersome structures may also complicate the procedure required to set up the mining sluice and may also hinder adjustment of the mining sluice to suit the conditions at a particular mining site. For example, it may be that a miner will discover that conditions at a particular mining site indicate the presence of relatively fine particulate valuable material (say, for example, gold dust as opposed to gold nuggets). Retention of such fine particulate valuable material by the mining sluice dictates the positioning of the tray(s) at a relatively small angle with respect to the horizontal to maximize the rejection of bulkier waste material from the mining sluice while retaining finer particulate valuable material in the mining sluice. Conversely, if the miner discovers that conditions at a particular mining site indicate the presence of relatively heavier particulate valuable material (say, for example, gold nuggets as opposed to gold dust) then it would be desirable to decrease the angle of the tray(s) with respect to the horizontal to avoid washing the relatively heavier valuable material completely through the mining sluice. If multiple trays are provided, then it may even be desirable to provide (for example) a relatively large angle of inclination on the uppermost tray and progressively smaller angles of inclination on lower trays in order to separate a range of sizes of particulate valuable materials from the raw material. Because conditions at different mining sites may differ (indeed, conditions may vary over time at a given mining site) it is desirable to provide means whereby the mining sluice may be adjusted quickly and efficiently to enable the operator to maximize retention of particulate valuable materials. Accordingly, a second object of the invention is to provide a mining sluice which may quickly and effectively be adjusted to vary the inclination of the tray(s) relative to the horizontal.
Another disadvantage of conventional mining sluices has been the relatively rapid build-up around the base of the mining sluice of a substantial quantity of waste material which interferes with the operation of the mining sluice. Accordingly, a further object of the invention is to provide deflection means for deflecting waste material away from the base of the mining sluice, resulting in less frequent need to clear away waste material from the base of the mining sluice.